Groovy example source code file (StatementWriter.java)

This example Groovy source code file (StatementWriter.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

blockrecorder, blockrecorder, compilestack, constantexpression, expression, expression, label, label, methodvisitor, methodvisitor, operandstack, runnable, statement, string, util

The Groovy StatementWriter.java source code

/*
 * Copyright 2003-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.codehaus.groovy.classgen.asm;

import java.util.Iterator;
import java.util.List;

import org.codehaus.groovy.ast.ClassHelper;
import org.codehaus.groovy.ast.ClassNode;
import org.codehaus.groovy.ast.Parameter;
import org.codehaus.groovy.ast.expr.ArgumentListExpression;
import org.codehaus.groovy.ast.expr.ClosureListExpression;
import org.codehaus.groovy.ast.expr.ConstantExpression;
import org.codehaus.groovy.ast.expr.EmptyExpression;
import org.codehaus.groovy.ast.expr.Expression;
import org.codehaus.groovy.ast.expr.MethodCallExpression;
import org.codehaus.groovy.ast.stmt.AssertStatement;
import org.codehaus.groovy.ast.stmt.BlockStatement;
import org.codehaus.groovy.ast.stmt.BreakStatement;
import org.codehaus.groovy.ast.stmt.CaseStatement;
import org.codehaus.groovy.ast.stmt.CatchStatement;
import org.codehaus.groovy.ast.stmt.ContinueStatement;
import org.codehaus.groovy.ast.stmt.DoWhileStatement;
import org.codehaus.groovy.ast.stmt.ExpressionStatement;
import org.codehaus.groovy.ast.stmt.ForStatement;
import org.codehaus.groovy.ast.stmt.IfStatement;
import org.codehaus.groovy.ast.stmt.ReturnStatement;
import org.codehaus.groovy.ast.stmt.Statement;
import org.codehaus.groovy.ast.stmt.SwitchStatement;
import org.codehaus.groovy.ast.stmt.SynchronizedStatement;
import org.codehaus.groovy.ast.stmt.ThrowStatement;
import org.codehaus.groovy.ast.stmt.TryCatchStatement;
import org.codehaus.groovy.ast.stmt.WhileStatement;
import org.codehaus.groovy.classgen.asm.CompileStack.BlockRecorder;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;

import static org.objectweb.asm.Opcodes.*;

public class StatementWriter {
    // iterator
    private static final MethodCaller iteratorNextMethod = MethodCaller.newInterface(Iterator.class, "next");
    private static final MethodCaller iteratorHasNextMethod = MethodCaller.newInterface(Iterator.class, "hasNext");
    
    private WriterController controller;
    public StatementWriter(WriterController controller) {
        this.controller = controller;
    }

    protected void writeStatementLabel(Statement statement) {
        String name = statement.getStatementLabel();
        if (name != null) {
            Label label = controller.getCompileStack().createLocalLabel(name);
            controller.getMethodVisitor().visitLabel(label);
        }
    }
    
    public void writeBlockStatement(BlockStatement block) {
        CompileStack compileStack = controller.getCompileStack();

        //GROOVY-4505 use no line number information for the block
        writeStatementLabel(block);
        
        int mark = controller.getOperandStack().getStackLength();
        compileStack.pushVariableScope(block.getVariableScope());
        for (Statement statement : block.getStatements()) {
            statement.visit(controller.getAcg());
        }
        compileStack.pop();

        controller.getOperandStack().popDownTo(mark);
    }

    public void writeForStatement(ForStatement loop) {
        Parameter loopVar = loop.getVariable();
        if (loopVar == ForStatement.FOR_LOOP_DUMMY) {
            writeForLoopWithClosureList(loop);
        } else {
            writeForInLoop(loop);
        }
    }
    
    protected void writeIteratorHasNext(MethodVisitor mv) {
        iteratorHasNextMethod.call(mv);
    }
    
    protected void writeIteratorNext(MethodVisitor mv) {
        iteratorNextMethod.call(mv);
    }
    
    protected void writeForInLoop(ForStatement loop) {
        controller.getAcg().onLineNumber(loop,"visitForLoop");
        writeStatementLabel(loop);
        
        CompileStack compileStack = controller.getCompileStack();
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();

        compileStack.pushLoop(loop.getVariableScope(), loop.getStatementLabel());

        // Declare the loop counter.
        BytecodeVariable variable = compileStack.defineVariable(loop.getVariable(), false);

        // Then get the iterator and generate the loop control
        MethodCallExpression iterator = new MethodCallExpression(loop.getCollectionExpression(), "iterator", new ArgumentListExpression());
        iterator.visit(controller.getAcg());
        operandStack.doGroovyCast(ClassHelper.Iterator_TYPE);

        final int iteratorIdx = compileStack.defineTemporaryVariable("iterator", ClassHelper.Iterator_TYPE, true);

        Label continueLabel = compileStack.getContinueLabel();
        Label breakLabel = compileStack.getBreakLabel();

        mv.visitLabel(continueLabel);
        mv.visitVarInsn(ALOAD, iteratorIdx);
        writeIteratorHasNext(mv);
        // note: ifeq tests for ==0, a boolean is 0 if it is false
        mv.visitJumpInsn(IFEQ, breakLabel);

        mv.visitVarInsn(ALOAD, iteratorIdx);
        writeIteratorNext(mv);
        operandStack.push(ClassHelper.OBJECT_TYPE);
        operandStack.storeVar(variable);

        // Generate the loop body
        loop.getLoopBlock().visit(controller.getAcg());

        mv.visitJumpInsn(GOTO, continueLabel);
        mv.visitLabel(breakLabel);

        compileStack.pop();
    }

    protected void writeForLoopWithClosureList(ForStatement loop) {
        controller.getAcg().onLineNumber(loop,"visitForLoop");
        writeStatementLabel(loop);

        MethodVisitor mv = controller.getMethodVisitor();
        controller.getCompileStack().pushLoop(loop.getVariableScope(), loop.getStatementLabel());

        ClosureListExpression clExpr = (ClosureListExpression) loop.getCollectionExpression();
        controller.getCompileStack().pushVariableScope(clExpr.getVariableScope());

        List expressions = clExpr.getExpressions();
        int size = expressions.size();

        // middle element is condition, lower half is init, higher half is increment
        int condIndex = (size - 1) / 2;

        // visit init
        for (int i = 0; i < condIndex; i++) {
            visitExpressionOrStatement(expressions.get(i));
        }

        Label continueLabel = controller.getCompileStack().getContinueLabel();
        Label breakLabel = controller.getCompileStack().getBreakLabel();

        Label cond = new Label();
        mv.visitLabel(cond);
        // visit condition leave boolean on stack
        {
            Expression condExpr = (Expression) expressions.get(condIndex);
            int mark = controller.getOperandStack().getStackLength();
            condExpr.visit(controller.getAcg());
            controller.getOperandStack().castToBool(mark,true);
        }
        // jump if we don't want to continue
        // note: ifeq tests for ==0, a boolean is 0 if it is false
        controller.getOperandStack().jump(IFEQ, breakLabel);

        // Generate the loop body
        loop.getLoopBlock().visit(controller.getAcg());

        // visit increment
        mv.visitLabel(continueLabel);
        for (int i = condIndex + 1; i < size; i++) {
            visitExpressionOrStatement(expressions.get(i));
        }

        // jump to test the condition again
        mv.visitJumpInsn(GOTO, cond);

        // loop end
        mv.visitLabel(breakLabel);

        controller.getCompileStack().pop();
        controller.getCompileStack().pop();
    }
    
    private void visitExpressionOrStatement(Object o) {
        if (o == EmptyExpression.INSTANCE) return;
        if (o instanceof Expression) {
            Expression expr = (Expression) o;
            int mark = controller.getOperandStack().getStackLength();
            expr.visit(controller.getAcg());
            controller.getOperandStack().popDownTo(mark);
        } else {
            ((Statement) o).visit(controller.getAcg());
        }
    }

    public void writeWhileLoop(WhileStatement loop) {
        controller.getAcg().onLineNumber(loop,"visitWhileLoop");
        writeStatementLabel(loop);

        MethodVisitor mv = controller.getMethodVisitor();

        controller.getCompileStack().pushLoop(loop.getStatementLabel());
        Label continueLabel = controller.getCompileStack().getContinueLabel();
        Label breakLabel = controller.getCompileStack().getBreakLabel();

        mv.visitLabel(continueLabel);
        Expression bool = loop.getBooleanExpression();
        boolean boolHandled = false;
        if (bool instanceof ConstantExpression) {
            ConstantExpression constant = (ConstantExpression) bool;
            if (constant.getValue()==Boolean.TRUE) {
                boolHandled = true;
                // do nothing
            } else if (constant.getValue()==Boolean.FALSE) {
                boolHandled = true;
                mv.visitJumpInsn(GOTO, breakLabel);
            }
        }

        if(!boolHandled) {
            bool.visit(controller.getAcg());
            controller.getOperandStack().jump(IFEQ, breakLabel);
        }

        loop.getLoopBlock().visit(controller.getAcg());

        mv.visitJumpInsn(GOTO, continueLabel);
        mv.visitLabel(breakLabel);

        controller.getCompileStack().pop();            
    }

    public void writeDoWhileLoop(DoWhileStatement loop) {
        controller.getAcg().onLineNumber(loop,"visitDoWhileLoop");
        writeStatementLabel(loop);

        MethodVisitor mv = controller.getMethodVisitor();

        controller.getCompileStack().pushLoop(loop.getStatementLabel());
        Label breakLabel = controller.getCompileStack().getBreakLabel();
        Label continueLabel = controller.getCompileStack().getContinueLabel();
        mv.visitLabel(continueLabel);

        loop.getLoopBlock().visit(controller.getAcg());

        loop.getBooleanExpression().visit(controller.getAcg());
        controller.getOperandStack().jump(IFEQ, continueLabel);
        mv.visitLabel(breakLabel);

        controller.getCompileStack().pop();
    }

    public void writeIfElse(IfStatement ifElse) {
        controller.getAcg().onLineNumber(ifElse,"visitIfElse");
        writeStatementLabel(ifElse);

        MethodVisitor mv = controller.getMethodVisitor();

        ifElse.getBooleanExpression().visit(controller.getAcg());
        Label l0 = controller.getOperandStack().jump(IFEQ);

        // if-else is here handled as a special version
        // of a boolean expression
        controller.getCompileStack().pushBooleanExpression();
        ifElse.getIfBlock().visit(controller.getAcg());
        controller.getCompileStack().pop();

        Label l1 = new Label();
        mv.visitJumpInsn(GOTO, l1);
        mv.visitLabel(l0);

        controller.getCompileStack().pushBooleanExpression();
        ifElse.getElseBlock().visit(controller.getAcg());
        controller.getCompileStack().pop();

        mv.visitLabel(l1);
    }

    public void writeTryCatchFinally(TryCatchStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitTryCatchFinally");
        writeStatementLabel(statement);
        
        MethodVisitor mv = controller.getMethodVisitor();
        CompileStack compileStack = controller.getCompileStack();
        OperandStack operandStack = controller.getOperandStack();

        Statement tryStatement = statement.getTryStatement();
        final Statement finallyStatement = statement.getFinallyStatement();

        // start try block, label needed for exception table
        Label tryStart = new Label();
        mv.visitLabel(tryStart);
        BlockRecorder tryBlock = makeBlockRecorder(finallyStatement);
        tryBlock.startRange(tryStart);

        tryStatement.visit(controller.getAcg());

        // goto finally part
        Label finallyStart = new Label();
        mv.visitJumpInsn(GOTO, finallyStart);

        Label tryEnd = new Label();
        mv.visitLabel(tryEnd);
        tryBlock.closeRange(tryEnd);
        // pop for "makeBlockRecorder(finallyStatement)"
        controller.getCompileStack().pop();

        BlockRecorder catches = makeBlockRecorder(finallyStatement);
        for (CatchStatement catchStatement : statement.getCatchStatements()) {
            ClassNode exceptionType = catchStatement.getExceptionType();
            String exceptionTypeInternalName = BytecodeHelper.getClassInternalName(exceptionType);

            // start catch block, label needed for exception table
            Label catchStart = new Label();
            mv.visitLabel(catchStart);
            catches.startRange(catchStart);

            // create exception variable and store the exception
            Parameter exceptionVariable = catchStatement.getVariable();
            compileStack.pushState();
            compileStack.defineVariable(exceptionVariable, true);
            // handle catch body
            catchStatement.visit(controller.getAcg());
            // place holder to avoid problems with empty catch blocks
            mv.visitInsn(NOP);
            // pop for the variable
            controller.getCompileStack().pop();

            // end of catch
            Label catchEnd = new Label();
            mv.visitLabel(catchEnd);
            catches.closeRange(catchEnd);

            // goto finally start
            mv.visitJumpInsn(GOTO, finallyStart);
            compileStack.writeExceptionTable(tryBlock, catchStart, exceptionTypeInternalName);
        }

        // Label used to handle exceptions in catches and regularly
        // visited finals.
        Label catchAny = new Label();

        // add "catch any" block to exception table for try part we do this 
        // after the exception blocks, because else this one would supersede
        // any of those otherwise
        compileStack.writeExceptionTable(tryBlock, catchAny, null);
        // same for the catch parts
        compileStack.writeExceptionTable(catches, catchAny, null);

        // pop for "makeBlockRecorder(catches)"
        compileStack.pop();

        // start finally
        mv.visitLabel(finallyStart);
        finallyStatement.visit(controller.getAcg());
        mv.visitInsn(NOP);  //**

        // goto after all-catching block
        Label skipCatchAll = new Label();
        mv.visitJumpInsn(GOTO, skipCatchAll);

        // start a block catching any Exception
        mv.visitLabel(catchAny);
        //store exception
        //TODO: maybe define a Throwable and use it here instead of Object
        operandStack.push(ClassHelper.OBJECT_TYPE);
        int anyExceptionIndex = compileStack.defineTemporaryVariable("exception", true);

        finallyStatement.visit(controller.getAcg());

        // load the exception and rethrow it
        mv.visitVarInsn(ALOAD, anyExceptionIndex);
        mv.visitInsn(ATHROW);

        mv.visitLabel(skipCatchAll);
    }
    
    private BlockRecorder makeBlockRecorder(final Statement finallyStatement) {
        final BlockRecorder block = new BlockRecorder();
        Runnable tryRunner = new Runnable() {
            public void run() {
                controller.getCompileStack().pushBlockRecorderVisit(block);
                finallyStatement.visit(controller.getAcg());
                controller.getCompileStack().popBlockRecorderVisit(block);
            }
        };
        block.excludedStatement = tryRunner;
        controller.getCompileStack().pushBlockRecorder(block);
        return block;
    }

    public void writeSwitch(SwitchStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitSwitch");
        writeStatementLabel(statement);

        statement.getExpression().visit(controller.getAcg());

        // switch does not have a continue label. use its parent's for continue
        Label breakLabel = controller.getCompileStack().pushSwitch();

        int switchVariableIndex = controller.getCompileStack().defineTemporaryVariable("switch", true);

        List caseStatements = statement.getCaseStatements();
        int caseCount = caseStatements.size();
        Label[] labels = new Label[caseCount + 1];
        for (int i = 0; i < caseCount; i++) {
            labels[i] = new Label();
        }

        int i = 0;
        for (Iterator iter = caseStatements.iterator(); iter.hasNext(); i++) {
            CaseStatement caseStatement = (CaseStatement) iter.next();
            writeCaseStatement(caseStatement, switchVariableIndex, labels[i], labels[i + 1]);
        }

        statement.getDefaultStatement().visit(controller.getAcg());

        controller.getMethodVisitor().visitLabel(breakLabel);

        controller.getCompileStack().pop();   
    }
    
    protected void writeCaseStatement(
            CaseStatement statement, int switchVariableIndex,
            Label thisLabel, Label nextLabel) 
    {
        controller.getAcg().onLineNumber(statement, "visitCaseStatement");
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();

        mv.visitVarInsn(ALOAD, switchVariableIndex);
        
        statement.getExpression().visit(controller.getAcg());
        operandStack.box();
        controller.getBinaryExpHelper().getIsCaseMethod().call(mv);
        operandStack.replace(ClassHelper.boolean_TYPE);

        Label l0 = controller.getOperandStack().jump(IFEQ);

        mv.visitLabel(thisLabel);

        statement.getCode().visit(controller.getAcg());

        // now if we don't finish with a break we need to jump past
        // the next comparison
        if (nextLabel != null) {
            mv.visitJumpInsn(GOTO, nextLabel);
        }

        mv.visitLabel(l0);
    }

    public void writeBreak(BreakStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitBreakStatement");
        writeStatementLabel(statement);

        String name = statement.getLabel();
        Label breakLabel = controller.getCompileStack().getNamedBreakLabel(name);
        controller.getCompileStack().applyFinallyBlocks(breakLabel, true);

        controller.getMethodVisitor().visitJumpInsn(GOTO, breakLabel);
    }

    public void writeContinue(ContinueStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitContinueStatement");
        writeStatementLabel(statement);

        String name = statement.getLabel();
        Label continueLabel = controller.getCompileStack().getContinueLabel();
        if (name != null) continueLabel = controller.getCompileStack().getNamedContinueLabel(name);
        controller.getCompileStack().applyFinallyBlocks(continueLabel, false);
        controller.getMethodVisitor().visitJumpInsn(GOTO, continueLabel);
    }

    public void writeSynchronized(SynchronizedStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitSynchronizedStatement");
        writeStatementLabel(statement);
        final MethodVisitor mv = controller.getMethodVisitor();
        CompileStack compileStack = controller.getCompileStack();

        statement.getExpression().visit(controller.getAcg());
        controller.getOperandStack().box();
        final int index = compileStack.defineTemporaryVariable("synchronized", ClassHelper.OBJECT_TYPE, true);

        final Label synchronizedStart = new Label();
        final Label synchronizedEnd = new Label();
        final Label catchAll = new Label();

        mv.visitVarInsn(ALOAD, index);
        mv.visitInsn(MONITORENTER);
        mv.visitLabel(synchronizedStart);
        // place holder for "empty" synchronized blocks, for example
        // if there is only a break/continue.
        mv.visitInsn(NOP);

        Runnable finallyPart = new Runnable() {
            public void run() {
                mv.visitVarInsn(ALOAD, index);
                mv.visitInsn(MONITOREXIT);
            }
        };
        BlockRecorder fb = new BlockRecorder(finallyPart);
        fb.startRange(synchronizedStart);
        compileStack.pushBlockRecorder(fb);
        statement.getCode().visit(controller.getAcg());

        fb.closeRange(catchAll);
        compileStack.writeExceptionTable(fb, catchAll, null);
        compileStack.pop(); //pop fb

        finallyPart.run();
        mv.visitJumpInsn(GOTO, synchronizedEnd);
        mv.visitLabel(catchAll);
        finallyPart.run();
        mv.visitInsn(ATHROW);

        mv.visitLabel(synchronizedEnd);
    }

    public void writeAssert(AssertStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitAssertStatement");
        writeStatementLabel(statement);
        controller.getAssertionWriter().writeAssertStatement(statement);
    }

    public void writeThrow(ThrowStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitThrowStatement");
        writeStatementLabel(statement);
        MethodVisitor mv = controller.getMethodVisitor();

        statement.getExpression().visit(controller.getAcg());

        // we should infer the type of the exception from the expression
        mv.visitTypeInsn(CHECKCAST, "java/lang/Throwable");
        mv.visitInsn(ATHROW);
        
        controller.getOperandStack().remove(1);
    }

    public void writeReturn(ReturnStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitReturnStatement");
        writeStatementLabel(statement);
        MethodVisitor mv = controller.getMethodVisitor();
        OperandStack operandStack = controller.getOperandStack();
        ClassNode returnType = controller.getReturnType();

        if (returnType == ClassHelper.VOID_TYPE) {
            if (!(statement.isReturningNullOrVoid())) {
                //TODO: move to Verifier
                controller.getAcg().throwException("Cannot use return statement with an expression on a method that returns void");
            }
            controller.getCompileStack().applyBlockRecorder();
            mv.visitInsn(RETURN);
            return;
        }

        Expression expression = statement.getExpression();
        expression.visit(controller.getAcg());
        
        if (controller.getCompileStack().hasBlockRecorder()) {
            ClassNode type = operandStack.getTopOperand();
            // value is always saved in boxed form, so no need to have a special load routine here
            int returnValueIdx = controller.getCompileStack().defineTemporaryVariable("returnValue", type, true);
            controller.getCompileStack().applyBlockRecorder();
            operandStack.load(type, returnValueIdx);
        }
        
        operandStack.doGroovyCast(returnType); 
        BytecodeHelper.doReturn(mv, returnType);
        operandStack.remove(1);
    }

    public void writeExpressionStatement(ExpressionStatement statement) {
        controller.getAcg().onLineNumber(statement, "visitExpressionStatement: " + statement.getExpression().getClass().getName());
        writeStatementLabel(statement);

        Expression expression = statement.getExpression();

        int mark = controller.getOperandStack().getStackLength();
        expression.visit(controller.getAcg());
        controller.getOperandStack().popDownTo(mark);
    }
}